Process for roll-compacting of metal powder with flange lubrication



Nov. 11, 1969 BUCHQVECKY ET AL 3,478,136

PROCESS FOR ROLL-COMPACTING OF METAL POWDER WITH FLANGE LUBRICATION Filed May 25, 1967 INVENTORS KALMAN E. BUCHOVECKY WILBUR L. PATTON ATTORNEY United States Patent U.S. C]. 264-111 1 Claim ABSTRACT OF THE DISCLOSURE When metal powders are roll-compacted to form a strip between a pair of mating rolls, one of which has flanges at its ends enclosing the ends of the other roll at close clearance, the metal powder tends to weld to such roll ends and flanges. This is avoided by continuously coating the inside face of each flange with a lubricant by means of a transfer wheel turning in contact with the flange and a source of lubricant.

BACKGROUND OF THE INVENTION Field of the invention The invention is in the field of powder metallurgy and more particularly the compaction of metal powders, by rolling, to form metal strip.

Description of the prior art When metal powder is compacted to strip between opposing rolls, there is a tendency for it to spill out at the ends of the roll gap, thus giving a sheet which is not compacted to the same density, coherence or thickness at the edges as in the middle. This leakage has been minimized by using as the compacting means a pair of rolls, one of which is recessed by providing it with a flange at each end and the other of which is not flanged and is mated to the first roll. The clearance must be close enough to restrain the compact so that lateral motion can take place only by extrusion. It is difficult to avoid leakage of powder or compact without developing a tendency for the powder particles to weld to the flange faces and for the strip to become wedged between the flanges, with the attendant difliculty of discharging it from the rolls.

In Lund et al. U.S. Patent 3,162,708 a method is proposed for solving the latter problem by mounting a flange, of greater diameter than the roll, at each end of one of the rolls but spaced a short distance from each opposing end of the roll so that there are relatively narrow spaces between the roll ends and the opposing flanges. While this technique may aid in effecting release of the strip from the flanged roll when rolling loads are comparatively low, the described flange spacing has little or no preventative effect on the tendency of the powder particles to weld to the opposing faces of the flange and mating roll ends.

SUMMARY OF THE INVENTION Now according to the present invention the foregoing and related problems of the prior art can be overcome, and metal powders can be roll-compacted to strip between a pair of mating rolls, one of which has flanges at its ends enclosing the ends of the other roll at close clearance, by processes in which a thin coating of a lubricant is continuously applied to an inside surface of a said flange during rotation thereof. It has further been found that the lubricant coating can be advantageously applied by means of a transfer wheel rotatably mounted in contact "ice with said inside flange surface and in contact with a source of lubricant.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a diagrammatic sketch, not to scale, of an apparatus of the invention in which there is a flanged roll 2 with inside flange face 1. A transfer wheel 3 is rotatably mounted with face 4 in contact with the flange face 1 and also in contact with face 6 of a lubricant supply line 5. The wheel and lubrication supply line are mounted on a carriage suspended on pivot 7, with an adjustable springloading mechanism 8 adapted to maintain contact between the wheel and flange under any desired pressure, and to accommodate end play in the flanged roll. In an alternative embodiment, not shown, the pivot 7 is located as far as practical from wheel face 4, with spring 8 being between the pivot and the applicator and operating under tension. In another specific embodiment, also not shown, the applicator mechanism is mounted in sliding grooves and is spring-loaded, so that parallelism between face 1 and face 4 is maintained despite lateral motion of the rolls.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus and processes of this invention are applicable to the rolling of strip from powders of various metals, including titanium, aluminum, zinc, lead, stainless steel, tool steel, copper, and metals of the group consisting of iron, cobalt and nickel in which there is dispersed a particulate refractory oxide, such as thoria, having an average particle size in the range of about 5 to millimicrons.

The invention is especially applicable to processes and mills for roll-compacting metal powders to strip wherein the powders are fed, as a mass in the shape of a blanket of predetermined width and of uniform or contoured thickness, to the nip between a pair of mating rolls, such nip being enclosed at its ends by flanges at each end of one of the rolls.

The clearance between the flanges and the ends of the mating roll is set close to minimize leakage of metal powder therethrough. With rolls 11.5 inches in diameter, for example, where the shoulders forming the flanges were 0.5 inch high, the flange-roll end clearance was set at 0.15 inch. This was minimum clearance permitted by the lateral roll motion or end-play of this pair of rolls. Using this clearance, coils of sound aluminium alloy strip were rolled from the corresponding alloy powder, provided the inside flanges were lubricated with a device of this invention. In contrast, when such lubrication was not used it was found that the flash (i.e., metal com pacted in the flange clearance) had a tendency to weld to the ends of the male roll, resulting in edge-cracking in the sheet. Without disturbances created by edge cracking, it was found that sound sheet could be produced at a minimum roll loading of 250,000 lbs., and freedom from center cracks was assured at 320,000 to 350,000 lbs.

In the transfer roll lubricators of the present invention, any of numerous lubricants commonly known in the art can be used. Preferably the lubricant is a liquid or paste or emulsion having sufficient viscosity to prevent it from running off the transfer wheel or being thrown off by centrifugal force. The lubricant can be a substance such as beeswax which is a solid at ordinary room temperatures but which becomes a liquid melt at the temperatures of powder rolling. Emulsions, solutions, or suspensions of substances which themselves are not ordinarily considered to be lubricants can often be used to advantage. In the latter category is a suspension of Teflon TFE fluorocarbon resin in amyl acetate,

commercially available as Emeralon 320, and this is a particularly preferred lubricant in processes of this invention.

It is of interest to note that Emeralon 320 was not a satisfactory lubricant if not continuously applied as a thin coating. When applied drop-wise by gravity from a tube immediately above the flange the flow could not be properly controlled, lubricant appeared on the roll face, and non-uniform sheet was produced. This illustrates also another advantage of the processes and apparatus of the present inventionnamely, that lubricant is transferred to the roll flanges only when the rolls are turning and thus excess lubrication cannot reach the roll.

Typical mill settings for rolling of aluminum alloy powder to sheet with the aid of lubrication according to this invention are as follows:

Sheet Coil No.

Mill gap (inches) Mill load (1135.)-.. Mill speed (IL/min.) Sheet thickness (inches) scrape off or cut off any metal particles which become welded to the rolls, especially at their edges, during powder roll compaction. Such scrapers can be mounted on the same carriage as the transfer roll, if desired.

We claim:

1. In a process for roll-compacting a metal powder to form a strip between a pair of mating rolls, one of which has flanges at its ends enclosing the ends of the other roll at close clearance, the improvement which comprises continuously applying a coating of a lubricant to a rotating member contacting an inside surface of each of said flanges to transfer a thin coating of said lubricant upon said flange surfaces during rotation thereof.

References Cited UNITED STATES PATENTS 2,530,503 11/1950 Bonham. 3,054,142 '9/ 1962 Hinderer et 211. 3,124,838 3/1964 Lund et al 189 ROBERT F. WHITE, Primary Examiner J. R. HALL, Assistant Examiner U.S. Cl. X.R. 18-9 

